JP2016177194A - Image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image projection device which has an excellent portability and can display an enlarged image easily and in good quality.SOLUTION: An image projection device comprises: a light source; an image display element which is illuminated by the light source; and a projection optical system which enlarges and projects an image formed in the image display element towards a projection target. The projection optical system has a dioptric system constituted of lenses and a reflection optical system which is provided with at least one reflection surface, and an image projected by the projection optical system has a different aspect ratio from the aspect ratio of the image display element.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image projection apparatus.

  There has been known an image projection apparatus that displays an image by enlarging and projecting image light generated according to data input from a connected information terminal toward a projection object. The image projection apparatus is called a projector. One type of projector is an ultra-short focus projector that has a short distance to a screen, which is a projection object.

  There is also a projector that can be connected to a portable information terminal such as a smartphone or a tablet information terminal that has become widespread in recent years. Hereinafter, the portable information terminal is simply referred to as a portable terminal.

  Mobile terminals have been increasing in size and functionality of display screens. However, there is a limit to increasing the size of the display screen. Therefore, it is difficult to use for people with low vision such as the elderly. Further, when viewing an image displayed on the display screen of the mobile terminal, the user holds the main body with either hand. Therefore, the screen display cannot be seen when both hands are closed.

  If a projector is connected to the portable terminal, the display screen can be enlarged, and the screen display can be seen without having a main body. However, projectors are not intended to be carried, and are less portable than smartphones.

  In general, the projector projects and displays image light on a flat screen. Therefore, when displaying information or the like by connecting a projector to a portable terminal while outdoors, moving, or working, it is necessary to perform it in a place with a flat screen. If it does so, the ease of a portable terminal will be impaired. If it projects on the curved place instead of a flat screen, the image displayed there will be distorted according to the form of a projection surface.

  A projector that converts an aspect ratio of an image that can be used to correct image distortion is known (see, for example, Patent Document 1).

  It is suitable if there is a projector that has a size and weight that can be attached to the human body, can use a part of the human body as the projection object, and does not distort the displayed image. If the advantage of the ultra short focus projector and the projector described in Patent Document 1 are combined to realize a projector having an optical system capable of projecting an image on the human body in the vicinity of the mounting position of the projector, the distortion of the image is reduced. There is a possibility that it can be corrected. However, in order to realize a projector that uses a part of the human body as a projection object, there are other problems to be solved.

  When a part of the human body is used as a projection object, the projection location is not a plane. If the projection object is an arm, the projection surface is curved. On the curved projection surface, the focus at the center and the edge of the display image is different. As a result, the image becomes unclear. Further, in order to display a sufficiently large image, further contrivance is required.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image projection apparatus that is excellent in portability, can easily display an enlarged image, and can improve the quality of the displayed image.

  The present invention is an image projection apparatus including a light source, an image display element illuminated by the light source, and a projection optical system that enlarges and projects an image formed on the image display element toward a projection object. The projection optical system includes a refractive optical system including a lens and a reflection optical system including at least one reflection surface, and an image projected by the projection optical system has an aspect ratio of the image display. The main feature is that it is different from the aspect ratio of the element.

  According to the present invention, it is excellent in portability, an image can be enlarged and displayed easily, and the quality of the displayed image can be improved.

It is an optical arrangement | positioning figure which shows the example of the optical engine with which embodiment of the image projection apparatus which concerns on this invention is provided. It is a schematic diagram showing an embodiment of an image projection device according to the present invention. It is the side view which looked at the projector which is embodiment of the image projection apparatus which concerns on this invention from the one side. It is the side view which looked at the said projector from the other side. It is a figure which contrasts the image display element with which the said projector is provided, and the dimension of the image which the said projector displays. It is an optical arrangement diagram for explaining an example of setting the numerical aperture of the projector. FIG. 6 is an optical arrangement diagram for explaining another setting example of the numerical aperture of the projector. FIG. 6 is an optical layout diagram for explaining still another example of setting the numerical aperture of the projector. FIG. 6 is an optical layout diagram for explaining still another example of setting the numerical aperture of the projector. It is a figure which shows the example of the light source 101 which the said projector has. It is a schematic diagram which shows the usage example of the said projector. It is sectional drawing which shows 1st Example of the said projector. It is sectional drawing which shows 2nd Example of the said projector. It is sectional drawing which shows 3rd Example of the said projector. It is sectional drawing which shows 4th Example of the said projector. It is a figure which shows the example of the dimension of the image display element in 4th Example of the said projector. It is a figure which shows the example of the dimension of the display screen in 4th Example of the said projector. It is an expanded sectional view which shows 3rd Example of the said projector. It is the schematic which shows another embodiment of the image projection apparatus which concerns on this invention.

  Hereinafter, embodiments of an image projection apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a side view of an essential part of an optical system provided in an image projection apparatus according to the present invention as seen from one direction.

● Configuration of image projection device ●
Configuration of Optical Engine In FIG. 1, the optical engine 100 roughly includes an illumination optical system and a projection optical system 108. The illumination optical system is an optical system for illuminating the DMD 107 that is an image display element with light emitted from the light source 101. The projection optical system 108 is an optical system for projecting the light reflected by the DMD 107 toward the screen 200 that is a projection object. As shown in FIG. 1, the projection optical system 108 includes a refractive optical system that is a part of the projection optical system 108 and an aperture stop 1081 that is disposed at the incident end of the refractive optical system. The refractive optical system constituting the projection optical system 108 is an axially symmetric coaxial optical system in which a plurality of optical elements share the optical axis LX.

  Hereinafter, the illumination optical system included in the optical engine 100 will be described. The light emitted from the light source 101 is condensed on the incident end of the integrator rod 103 by the reflector 102. The integrator rod 103 is a light pipe formed by combining four mirrors into a tunnel shape. The light incident on the integrator rod 103 is repeatedly reflected by the mirror surface in the integrator rod 103, and becomes light with a uniform light amount distribution and no unevenness at the exit end of the integrator rod 103. As the light source 101, an ultra-high pressure mercury lamp, a xenon lamp, a halogen lamp, or the like is used.

  The exit of the integrator rod 103 is regarded as a surface light source, and an image of this surface light source is converted into an effective image area of the DMD 107 as an image display element via the DMD illumination lens 104, the first folding mirror 105, and the second folding mirror 106. Generate in The DMD illumination lens 104 is an optical element for efficiently irradiating the effective image area of the DMD 107. The first folding mirror 105 is a flat mirror whose reflecting surface is a plane. The second folding mirror 106 is a curved mirror having a concave reflecting surface.

  The light emitted from the integrator rod 103 passes through the DMD illumination lens 104 and is reflected by the first folding mirror 105 in the diagonally lower right direction in FIG. 1 toward the second folding mirror 106. The light reflected by the second folding mirror 106 illuminates the surface of the DMD 107 and is reflected by a large number of micromirrors in the effective image area of the DMD 107, so that the reflected light beam as image projection light is on the second folding mirror 106 side. And then enters the projection optical system 108. A portion from the light source 101 to the second folding mirror 106 is referred to as an illumination optical system.

  By the illumination optical system, the DMD 107 is illuminated with illumination light having no light amount unevenness and has a uniform illuminance distribution. Therefore, a projection image that is an enlarged image also has a uniform illuminance distribution.

  The DMD 107 is an image display element including a large number of micromirrors. Each micromirror changes the tilt angle in the range of +12 degrees to -12 degrees. For example, when the angle of the minute mirror is −12 degrees, the illumination light reflected by the minute mirror enters the projection lens. This state is called an ON state. When the angle of the mirror is +12 degrees, the illumination light reflected by the minute mirror is prevented from entering the projection lens of the projection optical system 108. This state is called an OFF state.

  The micro mirror of the DMD 107 corresponds to a pixel of an image displayed on the screen 200. Therefore, by controlling the inclination angle of each micromirror of the DMD 107, projection light necessary for forming an image displayed on the screen 200, that is, projection image light, is projected onto the screen 200 via the projection optical system 108. Can do.

  Next, a projector 1 that is an embodiment of an image projection apparatus will be described with reference to FIGS. The optical engine 100 described above is mounted inside the projector 1. As shown in FIG. 2, the projector 1 is provided on a wristband 11 that is a ring-shaped main body that can be worn on the user's arm 1000, and on a side surface in the circumferential direction of the wristband 11, and the projection optical system 108 (FIG. Projection window 12 from which image light from (see) is emitted.

  The image light emitted from the projection window 12 is enlarged and projected on a part of the surface of the arm 1000. A region where an image is displayed by the projected image light is a display region 201. That is, an example of the projection object in the projector 1 is the surface of the arm 1000.

  When the state in which the projector 1 is mounted on the arm 1000 is viewed from the side as shown in FIG. 3, the distance in the height direction from the central portion in the short direction in the display area 201 which is the surface of the arm 1000 to the projection window 12. The first distance d0 is approximately equal to the thickness of the wristband 11.

  As shown in FIG. 4, when the projector 1 is viewed from the insertion opening direction of the arm 1000, an end portion in the short direction of the display area 201 (see FIG. 2) in which an image by light projected from the projection window 12 is displayed. A distance in the height direction to the projection window 12 is a second distance d1. The second distance d1 is longer than the first distance d0. This is because when the light emitted from the projection window 12 of the projector 1 goes in the circumferential direction of the wristband 11, the distance from the projection window 12 increases by the roundness in the short direction of the arm 1000.

  Here, the difference between the aspect ratio of the display area 201 and the aspect ratio of the DMD 107 (see FIG. 1) will be described with reference to FIG. As shown in FIG. 5, the dimension of the display area 201 in the short direction is s1, and the dimension in the long direction is m0. That is, the aspect ratio of the display area 201 is represented by s1: m0. Further, the dimension of the DMD 107 in the short direction is s0, and the dimension in the long direction is m0. As a result, the aspect ratio of the DMD 107 is expressed as s0: m0. Since the projector 1 uses the arm 1000 as a projection object, in the display region 201 corresponding to the screen 200, the dimension s1 in the short direction is longer than the dimension s0 of the DMD 107. That is, when the projector 1 is mounted and an image is displayed on the display area 201 of the arm 1000, the focus of the image may be disturbed in the short direction. Hereinafter, the aspect ratio is referred to as an aspect ratio.

● Characteristics of the projector 1 The projector 1 is devised so as not to cause the disturbance of the focus of the image as described above. Hereinafter, main features of the projector 1 will be described.

  The difference between the first distance d0 and the second separation d1 described above varies depending on the thickness of the arm 1000 of the individual wearing the projector 1. As the difference is larger, when focusing is performed based on the first distance d0, the position corresponding to the second distance d1, that is, the focal point at the short-side end of the display area 201 is disturbed. When the focus is disturbed, the displayed image becomes unclear.

  In general, if the projection distance is long, the depth of focus becomes deep. Therefore, so-called defocusing does not occur with the difference in distance from the projection window 12 at the short-side end and the short-side center of the display area 201. However, since the optical engine 100 is for performing ultra-short distance projection, the depth of focus is shallow and blurring is likely to occur.

  Therefore, the projector 1 uses a solid light source element for the light source 101 (see FIG. 1) of the optical engine 100. The solid light source element is, for example, a light emitting diode or a laser diode. By changing the light source 101 from the light source 101 to a solid light source element, the numerical aperture NA in the projection optical system 108 can be reduced.

  The NA is a parameter indicating the solid angle of a light beam taken into the projection optical system 108 (see FIG. 1) from an image display element such as the DMD 107. The NA will be described with reference to FIG. As shown in FIG. 6, in the optical engine 100, the light emitted from the light source 101 is reflected by the DMD 107 and enters the projection optical system 108. The incident optical path to the projection optical system 108 will be divided into two. One is a first light beam L1 that passes from the DMD 107 through the entrance of the projection optical system 108 and passes through the center of the aperture of the aperture stop 1081 that is an aperture window. The other is a second light beam L2 that passes from the DMD 107 through the entrance of the projection optical system 108 and reaches the end of the aperture of the aperture stop 1081, that is, the peripheral edge. The second light beam L2 spreads at an angle θ toward the opening end of the aperture stop 1081 with respect to the first light beam L1. The half value sine of the angle θ is NA. That is, NA is expressed by sin (θ / 2). As described above, the aperture stop 1081 defines the amount of light that enters the projection optical system 108 from the DMD 107.

  By making the light source 101 a solid light source element such as an LED, ie, a light emitting diode, or an LD, ie, a laser diode, the NA can be made 0.15 or less, for example. According to the configuration of the projector 1 described below, by reducing the NA, the depth of focus can be increased, and further, the decrease in the brightness of the image can be minimized. In the optical engine 100, when the liquid crystal element panel is used instead of the image display element in the DMD 107, the NA is 0.2 or more. If the tilt angle of the micro mirror of the DMD 107 is about 12 degrees, most NA is 0.2.

  If the NA is set to 0.15, the depth of focus can be expanded 1.3 times or more as compared with the optical engine 100 having an NA of 0.2. This makes it possible to obtain a depth of focus sufficient to cope with the roundness of the arm 1000.

  If the aperture stop 1081 provided in the projection optical system 108 of the optical engine 100 is stopped, the NA can be set small. As described above, the method of expanding the aperture depth by narrowing the aperture stop 1081 is the same as the method of increasing the depth of field by setting a large F value in the camera lens.

  When the NA is reduced, the amount of light incident on the projection optical system 108 from the DMD 107 decreases. When the amount of light to the projection optical system 108 decreases, the image displayed in the display area 201 becomes dark. Therefore, the projector 1 uses a solid light source element instead of the light source 101, thereby minimizing the reduction in brightness in the image.

  Hereinafter, a configuration for minimizing the decrease in the brightness of the display image while reducing the NA and increasing the depth of focus while using FIG. 6 to FIG. 10 will be described. First, the light L1 and the light L2 are compared using the optical engine 100 shown in FIG. In FIG. 6, the light beam L <b> 1 enters from the front surface of the integrator rod 103 and passes through the center of the aperture stop 1081 of the projection optical system 108. That is, the light beam L1 enters the integrator rod 103 from the front of the entrance. The light beam L2 passes through the end of the aperture stop 1081 of the projection optical system 108. The light beam L2 is incident on the integrator rod 103 obliquely from the entrance.

  As already described, the integrator rod 103 is an optical element that allows incident light to be regarded as a surface light source at the exit port while repeating total internal reflection. Accordingly, the light amount of the light beam L1 incident from the front of the entrance is small in the amount of light emitted from the integrator rod 103, and the sum of the light amounts of the light beam L2 incident from obliquely on the entrance is larger than the light amount of the light beam L1. .

  Next, a state in which the aperture stop 1081 is stopped in the optical engine 100 in order to reduce the NA will be considered. As shown in FIG. 7, when the aperture stop 1081 of the projection optical system 108 included in the optical engine 100 is stopped, the NA of the projection optical system 108 becomes small, and the surrounding light beam L2 is shielded. As a result, the amount of light L2 is significantly reduced.

  On the other hand, as shown in FIG. 8, when a solid light source 111 such as an LED or LD is used instead of the light source 101, the ratio of the light amount of the light beam L1 traveling forward from the solid light source 111 to the light amount of the peripheral light beam L2 is increased. Increase.

  As shown in FIG. 9, when the aperture stop 1081 of the projection optical system 108 provided in the optical engine 100 is stopped, the spread angle of the light beam L3 reaching the opening end of the aperture stop 1081 is narrowed to θ ′, and the NA is small. Become. Even if the NA is reduced in this way, the light source 101 can reduce the degree of light amount reduction compared to the light source 101.

  Next, the degree of light quantity reduction by using the solid light source 111 having a general Lambertian light distribution as the light source 101 will be described with reference to FIG. Note that the orientation distribution of the Lambert is a light distribution in which the energy held by the light beam traveling diagonally is proportional to cos α which is the cosine of the oblique emission angle α. is there.

  FIG. 10 is a diagram illustrating an example of the orientation distribution of the solid light source 111 that is a solid light source element. In FIG. 10, the length of the arrow line indicates the energy of the light beam, and the longer the arrow line, the stronger the light beam energy. Considering the light emitted from the center of the solid-state light source 111, the light energy in the front direction is the largest, and the light emitted in the oblique direction, that is, as the emission angle α becomes larger, the light energy becomes weaker. Such an orientation distribution is called a general Lambard distribution.

  Next, the difference in the incidence of light rays on the aperture stop 1081 in the optical engine 100 shown in FIGS. 8 and 9 when the NA value is changed will be described.

In the optical engine 100 shown in FIG. 8, when NA is set to 0.2, the value of θ is 23.07 degrees. Further, when NA is set to 0.15, θ ′ becomes 17.25 degrees.
Here, assuming that the angle α between the light beam L2 and the light beam L1 emitted from the solid-state light source 111 is 30 degrees, the energy of the light beam L2 with respect to the light beam L1 is a cosine of the angle α, so the value is 0.87. That is, the energy of the light beam L2 is 87% of the energy of the light beam L1.

  On the other hand, in the optical engine 100 shown in FIG. 9, the angle α ′ between the light beam L1 and the light beam L3 emitted from the solid light source 111 is smaller than the angle α between the light beam L2 and the light beam L1 shown in FIG. If calculation is performed on the assumption that θ = 23.07 degrees, θ ′ = 17.25 degrees, and α = 30 degrees, α ′ in FIG. 9 is 22 degrees. Since the energy of the light beam L3 with respect to the light beam L1 is a cosine of the angle α ′, its value is 0.93. That is, the energy of the light beam L3 is 93% of the energy of the light beam L1.

  By restricting the aperture stop 1081, the light beam L2 is shielded, but since the light bundle inside the light beam L3 emitted from the solid light source 111 remains, the reduction in the light amount is prevented by a minimum reduction. In contrast, when the light source 101 is used as in the optical engine 100 shown in FIG. 6, the energy ratio of the light beam L <b> 2 is high.

  As described above, the optical engine 100 uses the solid light source 111 as the light source 101, so that the NA can be reduced, the depth of focus can be increased, and the image can be prevented from becoming dark due to a decrease in the amount of light.

● Example of projector 1 ●
Hereinafter, an embodiment according to the projector 1 will be described. In the projectors 1 according to the first to fourth embodiments described below, the light source 101 includes the solid light source 111 and the NA is set to 0.15 or less. Note that the size of the DMD 107 included in the projector 1 according to the first to fourth embodiments is 0.1 inch, and the size of the image projected onto the display area 201 by the projector 1 is 4 inches.

  Here, the projection distance h0 and the band height K in the wristband 11 included in the specifications of the following embodiments will be described. In the vertical direction of the display area 201 shown in FIG. 12 or the like, that is, the Y direction, a point farthest from the display area 201 among the light rays reflected by the second mirror 1083 is defined as P1. Further, in the Y direction of the display area 201, a point closest to the display area 201 among the light rays reflected by the first mirror 1082 is defined as P2. The projection distance h0 is a distance between P1 and the display area 201 in the Y direction. The band height K in the wristband 11 is a distance between P1 and P2 in the Y direction. That is, the band height K is also the distance K.

Example 1
FIG. 11 is a schematic diagram illustrating an example of a state in which the projector 1 according to the first embodiment is mounted. FIG. 12 is an enlarged view of the projection optical system 108 in the projector 1 according to the first embodiment. In FIG. 11, the projection window 12 faces the back 1001 of the wearer's hand, not the arm 1000. In the projector 1, the optical engine 100 is housed in the wristband 11. In FIG. 11, only the projection optical system 108 of the optical engine 100 is shown. In FIG. 11, the projection optical system 108 also includes a mirror optical system for projecting toward the back 1001 of the refractive optical system.

  As shown in FIG. 12, in the projector 1, the image light formed by the DMD 107 passes through the refractive optical system that constitutes the projection optical system 108, and is reflected by the first mirror 1082 and the second mirror 1083 that constitute the mirror optical system. While enlarged. The enlarged image light is projected from the projection window 12 toward the back 1001 of the hand that is the projection object. As shown in FIG. 12, the coordinate axis in the projection optical system 108 according to each embodiment is the direction in which light travels from the DMD 107 to the projection optical system 108, and the direction parallel to the display area 201 is the Z direction. The direction perpendicular to the Z direction and the thickness direction of the wristband 11 is defined as the Y direction. The direction orthogonal to the Z direction and the Y direction is taken as the X direction. Therefore, FIG. 12 is a YZ sectional view of the projector 1.

Table 1 shows the specifications of the projection optical system 108 according to Example 1. In the projection optical system 108 according to the first embodiment, the projection distance h0 is set to 42 mm, the band height K of the wristband 11 that is a casing is set to 35 mm, and the NA is set to 0.1.

  In the projection optical system 108 according to the first embodiment, the NA is set to 0.1, so that the depth of focus can be made about twice as large as that in which the NA is set to 0.2. Even if the vertical distance from the second mirror 1083, which is an optical element having refractive power, to the display area 201 is set to a value larger than the projection distance h0, the occurrence of blurring can be suppressed. The second mirror 1083 is an optical element arranged between the projection optical system 108 and the display area 201 and is an optical element arranged on the side closest to the display area 201.

Example 2
Next, Example 2 will be described. FIG. 13 is a YZ sectional view of the projection optical system 108 in the projector 1 according to the second embodiment. In FIG. 13, in the projection optical system 108, a first mirror 1082 and a second mirror 1083 that constitute the mirror optical system are arranged at the subsequent stage of the refractive optical system. Table 2 shows the specifications of the projection optical system 108 according to Example 2. In the projection optical system 108 according to Example 2, the projection distance h0 is set to 33 mm, the band height K in the wristband 11 is set to 35 mm, and the NA is set to 0.1.

  In the projection optical system 108 according to the second embodiment, the NA setting is reduced to increase the depth of focus. Further, assuming that the user wears the projector 1 from above the clothing, the projection distance h0 is shortened by considering the thickness of the clothing.

  The projection optical system 108 according to the second embodiment sets the projection distance h0 to be shorter than the band height K in the wristband 11, and sets the size of the display area 201 at the position of the projection distance h0 to 4 inches. Thereby, even when clothes are worn, the size of the display area 201 is the same as that of the projection optical system 108 of the first embodiment.

Example 3
Next, Example 3 will be described. FIG. 14 is a YZ sectional view of the projection optical system 108 in the projector 1 according to the third embodiment. In FIG. 14, in the projection optical system 108, a first mirror 1082 and a second mirror 1083 that constitute the mirror optical system are arranged at the subsequent stage of the refractive optical system. Table 3 shows the specifications of the projection optical system 108 according to Example 3. In the projection optical system 108 according to Example 3, the projection distance h0 is set to 45 mm, the band height K in the wristband 11 is set to 34.3 mm, and the NA is set to 0.15.

  The projection optical system 108 according to Example 3 has a larger NA than the projection optical system 108 according to Example 1. Even if NA is increased as in the present embodiment, the band height K and the projection distance h0 in the wristband 11 can be set to substantially the same value.

  In the projector 1 including the projection optical system 108 according to the third embodiment, the amount of light of the projected image is increased as compared with the first and second embodiments. On the other hand, the depth of focus becomes shallow, and the range corresponding to roundness and unevenness in the user's arm 1000 becomes narrow. However, if the person has a small roundness of the arm 1000, the advantage of the projector 1 including the projection optical system 108 according to the first embodiment is great.

  Further, in the projection optical system 108 according to Example 3, as shown in FIG. 18, each lens of the projection optical system 108 is rotationally symmetric with respect to the optical axis LX.

Example 4
Next, Example 4 will be described. FIG. 15 is a YZ sectional view of the projection optical system 108 provided in the projector 1 according to the fourth embodiment. In FIG. 15, the projection optical system 108 is provided with a first mirror 1082 and a second mirror 1083 that constitute the mirror optical system after the refractive optical system. Table 4 shows the specifications of the projection optical system 108 according to Example 4. In the projection optical system 108 according to Example 4, the projection distance h0 is set to 33.6 mm, the band height K in the wristband 11 is set to 34 mm, and the NA is set to 0.1. Further, the aspect ratio of the projected image, which is the aspect ratio of the display area 201, is 15:10, and the aspect ratio of the DMD 107 is 16:10.

  An example of the aspect ratio of the DMD 107 according to the present embodiment is shown in FIG. FIG. 17 shows the aspect ratio of the display area 201 that is the aspect ratio of the image projected by the DMD 107 according to the present embodiment. As shown in FIG. 16, the DMD 107 has a horizontal dimension s0 of 2.14 mm and a vertical dimension m0 of 1.33 mm. Therefore, the aspect ratio of DMD 107 is 16:10. When this is enlarged and projected using a coaxial axisymmetric optical system, the aspect ratio of the displayed image is naturally 16:10. As already described, the projector 1 is attached to the arm 1000, and the display area 201 is not a plane. Therefore, ingenuity is required to display an image with the same aspect ratio as that of the DMD 107.

  Therefore, in the projection optical system 108 according to Example 4, the second mirror 1083 is a non-axisymmetric free-form surface mirror. (See FIG. 15). As a result, the aspect ratio of the projected image can be set to 15:10 as shown in FIG.

  The image size in the horizontal direction is smaller than that of the DMD 107. In this case, if the image is projected onto a flat screen, the displayed image is compressed in the horizontal direction. However, if the projector 1 projects an image on a rounded portion such as the arm 1000, the horizontal width of the image is expanded, so that a natural image is obtained.

  Note that the horizontal length of the DMD 107 is X0, and the vertical length of the DMD 107 is Y0. In addition, the horizontal length of the display area 201 is X1, and the vertical length of the display area 201 is Y1. In this case, the condition (X0 / Y0> X1 / Y1) is satisfied. Each length in the vertical direction is a length in a cross section including a perpendicular line of the optical axis LX of the projection optical system 108 and a perpendicular line of the display area 201. Each length in the horizontal direction is a length in a direction perpendicular to the vertical direction.

Example 5
Next, Example 5 will be described. FIG. 19 shows an example in which the mirror optical system constituting the reflection optical system included in the projection optical system 108 is configured by only the second mirror 1083. As shown in FIG. 19, the projection optical system 108 according to the present embodiment differs from the first to fourth embodiments in which the optical axis of the refractive optical system is substantially parallel to the length direction of the arm 1000. The axis is in the normal direction of the arm 1000. Thereby, the plane mirror of the reflective optical system that is necessary in the projection optical system 108 of Examples 1 to 4 can be omitted.

  In the projector 1 according to the fifth embodiment, since the longitudinal direction of the projection optical system 108 is the normal direction of the arm 1000, the band height K corresponding to the thickness of the wristband 11 becomes long. However, the number of components can be reduced as compared with the first to fourth embodiments, and the brightness can be improved.

  As described above, since the projector 1 has a shape that can be attached to the wrist, it is excellent in portability and can easily display a large image. Further, it is possible to correct the distortion of the projection image caused by the roundness around the wrist. Furthermore, even when worn over clothes, the screen size is not reduced, and a brighter image can be displayed. It is extremely portable and useful when necessary in conjunction with a portable information terminal.

Numerical Example in Each Example Next, specific numerical examples in the projection optical system 108 according to Examples 1 to 4 will be described. Table 5 shows a comparison between each example and a table showing each numerical example.

  In the description in Table 5, the interval (* 1) is an interval along the Z direction in FIG. Further, the eccentricity (* 2) is the amount of eccentricity along the Y direction in FIG. 12, that is, the amount of axial deviation.

Numerical Example According to First Embodiment First, a numerical example according to the first embodiment is shown. Table 6 shows configuration data indicating the radius of curvature, interval, refractive index, eccentricity, and the like of the lens.

  Surfaces 4, 15, 16, 17, and 18 in Table 6 are aspherical surfaces. These aspherical coefficients are shown in Table 7.

The formula for calculating the aspheric shape by applying the aspheric coefficient is the following formula 1.
(Formula 1)

Table 8 shows data relating to the layout of the first mirror 1082 that is a plane mirror, the second mirror 1083 that is a concave mirror, and the screen 200.

Table 9 shows free-form surface coefficients for forming the reflection surface of the second mirror 1083.

Formula 2 for calculating the reflection surface of the second mirror 1083 by applying the coefficients shown in Table 9 is shown in Formula 2.
(Formula 2)

  In Table 10, “**” means a power operation. “*” Means multiplication.

Numerical Example According to Second Embodiment Next, a numerical example according to the second embodiment is shown. Table 6 shows configuration data indicating the radius of curvature, interval, refractive index, decentration (* 2), and the like of the lens.

  Surfaces 4, 15, 16, 17, and 18 in Table 11 are aspherical surfaces. These aspherical coefficients are shown in Table 11.

  The equation for calculating the aspheric shape by applying the aspheric coefficient is the same as the equation 1 shown in the first embodiment.

Table 12 shows data relating to the layout of the first mirror 1082 that is a plane mirror, the second mirror 1083 that is a concave mirror, and the screen 200.

Table 13 shows free-form surface coefficients for forming the reflection surface of the second mirror 1083.

  An equation for calculating the reflection surface of the second mirror 1083 by applying the coefficient shown in Table 13 is the same as the equation 2 shown in the first embodiment.

  In Table 13, “**” means a power operation. “*” Means multiplication.

Numerical Example According to Example 3 Next, a numerical example according to Example 3 is shown. Table 14 shows configuration data indicating the radius of curvature, interval, refractive index, and eccentricity of the lens.

  Surfaces 4, 15, 16, 17, and 18 in Table 14 are aspherical surfaces. These aspheric coefficients are shown in Table 15.

  The equation for calculating the aspheric shape by applying the aspheric coefficient is the same as the equation 1 shown in the first embodiment.

Table 16 shows data relating to the layout of the first mirror 1082 that is a plane mirror, the second mirror 1083 that is a concave mirror, and the screen 200.

Table 17 shows free-form surface coefficients for forming the reflection surface of the second mirror 1083.

  An equation for calculating the reflecting surface of the second mirror 1083 by applying the coefficients shown in Table 17 is the same as the equation 2 shown in the first embodiment.

  In Table 17, “**” means a power operation. “*” Means multiplication.

Numerical Example According to Example 4 Next, a numerical example according to Example 4 is shown. Table 18 shows configuration data indicating the radius of curvature, interval, refractive index, eccentricity, and the like of the lens.

  Surfaces 4, 15, 16, 17, and 18 in Table 18 are aspherical surfaces. These aspheric coefficients are shown in Table 19.

  The equation for calculating the aspheric shape by applying the aspheric coefficient is the same as the equation 1 shown in the first embodiment.

Table 20 shows data relating to the layout of the first mirror 1082 that is a plane mirror, the second mirror 1083 that is a concave mirror, and the screen 200.

Table 21 shows free-form surface coefficients for forming the reflection surface of the second mirror 1083.

  An equation for calculating the reflecting surface of the second mirror 1083 by applying the coefficients shown in Table 21 is the same as the equation 2 shown in the first embodiment.

  In Table 21, “**” means a power operation. “*” Means multiplication.

  As described above, the image display apparatus according to the present invention can display a large-screen image on the screen from a very close distance by adjusting the condensing position of the highly divergent projection light beam.

1 Projector 11 Wristband 100 Optical Engine 101 Light Source 107 DMD
108 Projection Optical System 201 Display Area 1082 First Mirror 1083 Second Mirror

JP 2013-03566 A

Claims (7)

A light source;
An image display element illuminated by the light source;
A projection optical system for enlarging and projecting an image formed on the image display element toward a projection object,
The projection optical system includes a refractive optical system including a lens, and a reflective optical system including at least one reflective surface,
The image projected by the projection optical system has an aspect ratio different from the aspect ratio of the image display element.
An image projection apparatus characterized by that. The projection optical system has at least one non-axisymmetric Y optical element,
Due to the non-axisymmetric optical element, the projected image has an aspect ratio different from the aspect ratio of the image display element.
The image projection apparatus according to claim 1. The refractive optical system is an axially symmetric optical system in which a plurality of optical elements share an optical axis,
The horizontal length of the image display element is X0,
The vertical length of the image display element is Y0,
When the projection object is a flat screen, the horizontal length of the image projected on the flat screen is X1,
When the projection object is a flat screen, the vertical length of the image projected on the flat screen is Y1,
The length in the cross section including the vertical line of the optical axis and the vertical line of the flat screen;
The length in the vertical direction with respect to the vertical direction,
When
Satisfies the condition X0 / Y0> X1 / Y1.
The image projection apparatus according to claim 1. The refractive optical system is an axially symmetric coaxial optical system in which a plurality of optical elements share an optical axis,
The refractive optical system has an aperture stop that defines the amount of light incident from the image display element,
The refractive optical system has a numerical aperture of 0.15 or less.
The image projection apparatus according to claim 1. The projection optical system has an aperture window;
The reflective optical system includes a first mirror and a second mirror,
5. The image projection apparatus according to claim 1, wherein one of the first mirror and the second mirror is a non-axisymmetric concave mirror. The second mirror is a non-axisymmetric concave mirror;
When the projection object is a flat screen,
The projection distance h0, which is the distance between the point farthest from the plane screen among the rays reflected by the second mirror in the vertical direction of the plane screen and the plane screen,
Of the light rays reflected by the second mirror in the vertical direction of the flat screen, the point farthest from the flat screen and the light rays reflected by the first mirror in the vertical direction of the flat screen on the flat screen Shorter than the distance K, which is the distance to the nearest point,
The image projection apparatus according to claim 5. The refractive optical system is an axially symmetric coaxial optical system in which a plurality of optical elements share an optical axis,
The projection object is a flat screen,
The long side of the image projected on the flat screen is in a cross section including the normal of the flat screen and the optical axis of the coaxial optical system,
The short side of the image is in a direction perpendicular to the cross section of the long side,
The image projection apparatus according to claim 1.